Traditional braking systems for motor vehicles include conventional hydraulic or pneumatic brakes associated with two or more wheels of the vehicle. Such conventional brakes are actuated by pressurized fluid or compressed air. When actuated, the brakes exert a force on a disk or drum which spins in conjunction with the wheel of the vehicle in order to create frictional forces which resist rotation of the wheel. Traditionally, control signals have been transmitted to each of the brake system's actuators mechanically, or by a hydraulic or pneumatic control circuit. However, it has more recently been proposed to employ a centralized control unit to generate electronic control signals and to use such electronic control signals to control actuation of a vehicle's brakes. This type of electronic control scheme has become even more prevalent in view of modern brake systems which now often include not only conventional hydraulic or pneumatic brake actuator functionality, but also supplemental electronic functions such as antilock protection (ABS) and/or electronic braking force distribution (EBV) between the front and rear axles.
In some brake systems employing electronic control, it is known to employ distributed electronic control units to receive electronic control signals from the central control unit and to control the actuation of brake components in response thereto. Such distributed electronic control units may be associated with each individual brake component and/or may be associated with two or more brake components (for example, one distributed electronic control unit may be associated with both brake actuators on a single axle). In either case, the central control unit generates and transmits electronic control signals to each of the distributed electronic control units via one or more control networks, and the distributed electronic control units, in response to such electronic control signals, cause the brake component(s) with which they are associated to actuate. Such a system, however, suffers from a number of disadvantages. One disadvantage of such a system is that all brake components must be responsive to a single control signal, as there is no way for control signals intended for controlling only one brake component or group of brake components to be differentiated from those control signals intended for controlling another brake component or group of brake components.
This disadvantage is obviated by certain brake systems which employ a scheme for the recognition of the physical position of each individual brake component or each group of brake components. Known schemes of this type generally involve the manual programming or setting of a unique identifier in the memory of each distributed electronic control unit, which identifier is indicative of the physical position of the brake component or group of brake components with which the distributed electronic control unit is associated. In these systems, each of the control signals generated by the central control unit includes an indication of the identifier of the distributed control unit for which that control signal is intended. When each distributed electronic control unit receives the control signals, it determines, based upon the identifier contained in each control signal, whether that particular control signal is intended for it, and if so, responds accordingly. If that particular control signal is not intended for it, the control signal is ignored.
For example, the distributed electronic control unit associated with a brake component on the right front wheel of a vehicle may be programmed with an identifier indicative of such a position. Thus, when control signals are received from the central control unit, the distributed electronic control unit associated with a brake component on the right front wheel of the vehicle responds to the control signal only if that control signal includes the appropriate identifier (if not, the control signal is ignored). Distributed electronic control units associated with groups of brake components (e.g., the brake components on a vehicle axle) may be similarly programmed and controlled.
While the above-described control scheme allows each individual brake component or each group of brake components to be independently controlled by the central control unit, it does still suffer from a number of disadvantages. More specifically, the manual programming or setting of the unique identifier in the memory of each distributed electronic control unit may create compatibility problems, which may lead the brake system to operate inefficiently or even fail completely. This is true because each time a distributed electronic control unit is replaced and/or its location in the system is changed, the distributed electronic control unit must be manually programmed or reprogrammed. For example, if a brake component including a distributed electronic control unit failed and was replaced, the new brake component must be programmed with the identifier appropriate for its location. If the service technician overlooks such programming or programs the distributed electronic control unit incorrectly, that brake component may not respond at all, or may respond at inappropriate times.
A similar problem may occur if the locations of two or more brake components are switched. For example, if the left front and right front brake components are switched during servicing and not reprogrammed, the control signals generated by the central control unit intended to control the left front brake component would actually be controlling the right front brake component, while the control signals intended to control the right front brake component would actually be controlling the left front brake component. This could cause a hazardous condition during vehicle operation. Moreover, even if programming and/or reprogramming is carried out correctly, the process may be time-consuming and would likely require additional knowledge on the part of service technicians who service the brake system.
What is desired, therefore, is an electronically controlled braking system intended for use with wheeled vehicles which incorporates distributed electronic control units, which allows for the control of each individual brake component or each group of brake components associated with each distributed electronic control unit independently of those associated with other distributed electronic control units, which allows for control signals intended for controlling only one brake component or group of brake components to be differentiated from those control signals intended for controlling another brake component or group of brake components, which does not require that the distributed electronic control unit be manually programmed or reprogrammed each time a distributed electronic control unit is replaced and/or its location in the system is changed, and which employs an identification scheme, the implementation of which is not time-consuming and/or does not require additional knowledge on the part of service technicians who service the brake system.